For some reason every time I print it stops after a few minutes giving me an error 0, also the temperature shoots up in the graph and the whole machine stops...
I read on the internet this is because its reading too high of a temperature for the extruder, but I'm using the stock merlin firmware.
Can someone tell me what could be the problem? I do know I always get tonnes of errors in the cura term, could this mean the firmware can be corrupt too if my USB connection is so dodgy?
I hope someone can help me, I can't print right now...

All of my engines were pretty hot while printing, but I was only concerned about my extruder stepper motor, it was just barely possible to touch it.
Instead of reducing the current, I remembered having an old (small) PC fan laying around, and wanted to hook this up to the printer.
The fan is mounted to a bracket, which is in turn mounted on the ultimaker. The power is being sourced by the 19V LED output, but I'm using a LM317 to reduce that voltage to about 14 volts.
This setup has exceeded my expectations, even at long prints the motor only feels a little warm to the touch, WAY less than any of the other steppers.
As you can see, this is just a work in progress I just slapped together. If anyone has other ways of cooling their steppers, let me know!

Yeah I had the same issues 2 days ago, some parts were just not getting enough fill. The feeding mechanism was making cracking sounds, so I checked it out. Turns out I actually had some screws in the feeding mechanism way too tight, causing the wheel (with the bearing in it) to not being able to move. Eventually I loosened up that part, and made sure the feeder screw was nice and tight (but not too tight ofcourse)
I think you should first check your feeding mechanism, do a test print, and see if the filament sometimes stops going into the extruder. Once your feeder is okay, check your filament diameter in Cura, and maybe set the flow% to 110 percent to see if that helps.
Good luck!

I should get my camera back tonight, then I'll snap some pictures. In the meantime I'll try to explain how it looks.
I've had my Ultimaker only for a few days, so the belts are still very tight. But I do notice subtle signs of underextrusion on some parts of my print. I think this is also due to my filament thickness being just a little thinner then I specified in Cura. My digital calipers should arrive tomorrow or the day after, so I wouldn't be suprised if it's just a little bit thinner than 2.85 mm.....
I am looking at some of my previous prints... and I can see that on one side of the prints, lines are a little more 'tight' than the other side. I would really love to get some feedback on this because I'm so new to printing accuracy and stuff like that. I'll get pictures as soon as possible.

I'm noticing that I see a lot of errors in the terminal of the printing screen, they look like this:
echo:Unknown command: "" echo:Active Extruder: 0 Error:checksum mismatch, Last Line: 4 Error:Line Number is not Last Line Number+1, Last Line: 4 Error:No Line Number with checksum, Last Line: 4 Error:Line Number is not Last Line Number+1, Last Line: 4 Error:Line Number is not Last Line Number+1, Last Line: 4 Error:No Line Number with checksum, Last Line: 4 Error:Line Number is not Last Line Number+1, Last Line: 4 Error:No Line Number with checksum, Last Line: 4 Error:Line Number is not Last Line Number+1, Last Line: 4 Error:No Line Number with checksum, Last Line: 4 Error:Line Number is not Last Line Number+1, Last Line: 4 Error:Line Number is not Last Line Number+1, Last Line: 5 Error:Line Number is not Last Line Number+1, Last Line: 5 Error:Line Number is not Last Line Number+1, Last Line: 5 Error:Line Number is not Last Line Number+1, Last Line: 5 Error:Line Number is not Last Line Number+1, Last Line: 5 echo:Unknown command: "5" Error:No Line Number with checksum, Last Line: 5 Error:Line Number is not Last Line Number+1, Last Line: 6 Error:No Line Number with checksum, Last Line: 6 Error:checksum mismatch, Last Line: 22 Error:Line Number is not Last Line Number+1, Last Line: 22 Error:checksum mismatch, Last Line: 55 Error:No Line Number with checksum, Last Line: 55 Error:No Checksum with line number, Last Line: 85 Error:Line Number is not Last Line Number+1, Last Line: 85
How bad are these errors? What causes them?
I hope someone can clarify

Whenever I print with my ultimaker I notice my inner and outer walls are not touching. I usually print with an 0.8mm shell thickness, which causes 2 layers to form the shell. But for some reason there is a super tiny gap between them... Does anyone know how I could fix this?

I've been having problems with some prints that require retraction. I'm currently using 40mm/s retraction speed and 4.5mm of length.
Sometimes when I print with retraction, I notice gaps in some parts of my print. I think this happens because the filament isn't through the nozzle yet after the retraction ends... Also I'm noticing a subtle grinding noise coming from the bowden tube everytime it retracts... Is this normal?
I have found that I can usually get rid of the gaps by heating the PLA to 225 degrees, but I would love to get some feedback from a more experienced user.
Greetings,
Nick